The present invention relates to preparing of a manufacturing plan in a factory and, more particularly, to a method for preparing a manufacturing plan to thereby determine assignment of each of a plurality of manufacturing equipments to each of a plurality of manufacturing processes in a factory in which these manufacturing equipments are used in these manufacturing processes.
There have been proposed a few methods of preparing a production plan or of production management for securely achieving a predetermined amount of production by a delivery date by effectively utilizing the facilities in a factory.
For example, Japanese Unexamined Patent Publication No. Hei. 4-176546 discloses a production management method to assure a required product output by a delivery date. In the method of this publication, a target amount necessary to achieve the production of the required amount by the delivery date is set and, if an actual completed amount of production falls short of this target amount, an alarm will be output.
In addition, Japanese Unexamined Patent Publication No. Hei. 11-267951 proposes a method for preparing a production plan for a manufacturing factory wherein facilities thereof are desired to be continuously operated around the clock. According to this production plan preparing method of Japanese Unexamined Patent Publication No. Hei. 11-267951, in a predetermined production period (e.g., one week), first the facilities are operated continuously to accelerate the production and then stop the facilities in the latter part of the production period, thus restricting the number of stopping times of the operation of the facilities to one time for each production period.
Incidentally, each factory is usually provided with a plurality of manufacturing equipments, each of which is available for a plurality of manufacturing processes in many cases. Such an example is shown in FIG. 10. In the example of FIG. 10, a manufacturing equipment Ml is available for manufacturing processes P1, P3, and P4, while a manufacturing equipment M2 is available for manufacturing processes P1 and P2.
In such a case, the capability of the factory for processing each manufacturing process depends on how to assign each of the manufacturing equipment to the manufacturing processes, that is, for which manufacturing processes manufacturing equipments are available. Furthermore, in other words, the assignment of each manufacturing equipment must be determined so as to match the load of each manufacturing process by, for example, assigning more manufacturing equipments to a manufacturing process having a larger load.
However, neither of the above-mentioned production management method disclosed in Japanese Unexamined Patent Publication No. Hei. 4-176546 and the production plan preparing method disclosed in Japanese Unexamined Patent Publication No. Hei. 11-267951 takes into account the assignment of the manufacturing equipment to each of the manufacturing processes, so that capability for each manufacturing process is always constant. Therefore, they cannot accommodate a factory in which a large variety of products are manufactured and the load on each manufacturing process fluctuates with a customer""s order for each product, as in today""s semiconductor manufacturing factory, thus being deficient in versatility as methods for production management and production plan preparation.
Further, they do not take into account a fluctuation in load and capability and so cannot know previously at which of a plurality of manufacturing processes an imbalance between load and throughput becomes significant, thus finding it difficult to utilize the manufacturing equipment efficiently. There is, therefore, a need to preserve rather a lot of semi-finished products in process in order not to stop the manufacturing equipment, which is often accompanied by an awkward situation in which assignment of the manufacturing equipment is changed only after an imbalance occurs between load and throughput.
It is an object of the present invention to assign, in a manufacturing factory provided with a plurality of manufacturing processes and a plurality of manufacturing equipments, each of the equipment to these processes according to the work load of each process, thereby utilizing the manufacturing equipments effectively to process the work load.
It is another object of the present invention to comprehend previously about the throughput capability for each manufacturing process and the work load of the day to thereby enable deciding adoption or rejection of further loading and also discussing how to cope with overload previously.
To achieve the above objects, therefore, in a manufacturing factory charged with a plurality of manufacturing processes and having a plurality of manufacturing equipments each of which is available to the plurality of manufacturing processes, a method for preparing a manufacturing plan according to the present invention determines an assignment of the manufacturing equipment to the manufacturing processes through the following steps. Firstly, a manufacturing equipment is temporarily assigned to each of the manufacturing processes to determine a supposed operation pattern for the day. Then, work load of each manufacturing process of the day is allotted among the manufacturing equipments assigned to the manufacturing process. Thereafter, total load of each manufacturing equipment is calculated by summing up the work load allotted from the manufacturing processes. Using the total load thus calculated, a capability index of each manufacturing equipment is determined by dividing capacity of the manufacturing equipment of the day by the total load of the manufacturing equipment. Then, the capability index of the manufacturing equipment is multiplied with the work load allotted from the manufacturing process to the manufacturing equipment to provide a feasible load of the manufacturing equipment for the manufacturing process. By summing up the feasible load of each manufacturing equipment, a total feasible load of the day under the above supposed operation pattern is calculated for each manufacturing process. By comparing the total feasible load with the work load of the day for each manufacturing process, the supposed operation pattern is determined whether acceptable or not.
In a manufacturing factory charged with a plurality of manufacturing processes and having a plurality of manufacturing equipments each of which is available to the plurality of manufacturing processes, moreover, a method for preparing a manufacturing plan according to the present invention determines an assignment of the manufacturing equipment to the manufacturing processes through the following steps. Firstly, the manufacturing equipment is assigned to the manufacturing processes to determine an operation pattern for the day. Then, work load of each manufacturing process of the day is allotted among the manufacturing equipment assigned to the manufacturing process. Thereafter, total load of each manufacturing equipment is calculated by summing up the work load allotted from the manufacturing processes. Using the total load thus calculated, a capability index of each manufacturing equipment is determined by dividing capacity of the manufacturing equipment of the day by the total load of the manufacturing equipment. Then, the capability index of the manufacturing equipment is multiplied with the work load allotted from the manufacturing process to the manufacturing equipment to provide a feasible load of the manufacturing equipment for the manufacturing process. By summing up the feasible load of each manufacturing equipment, a total feasible load of the day under the above operation pattern is calculated for each manufacturing process. The above steps are repeated for all possible operation patterns in which assignment of the manufacturing equipment are different each other. For all the possible operation patterns, the total feasible load thus calculated is compared with the work load of the day for each of the manufacturing processes. The possible operation pattern, in which difference between the total feasible load and the work load of the day is the smallest, is adopted as the operation pattern for the day.
Further, a method for manufacturing semiconductor products according to the present invention is characterized in that the method for preparing a manufacturing plan according to the present invention is applied thereto.
According to the present invention, it is possible to calculate, in a manufacturing factory provided with a plurality of manufacturing processes and a plurality of manufacturing equipments, the manufacturing capability for each of these processes easily and rapidly, thereby appropriately assigning these equipment to each of these processes. It is, therefore, possible to efficiently utilize the manufacturing equipment without imbalance between the load and the capability for each of the manufacturing processes even in such a manufacturing factory that the load for each of these processes would fluctuate with a customer""s order for each product.
Further, according to the present invention, it is possible to refer the manufacturing capability and the load for each manufacturing process at the same time to thereby discuss previously an assignment of the manufacturing equipment for the day or the next day onward. Also, it is possible, for example, to focus particularly on management for such a manufacturing process that has a large ratio of the load against the capability, thus securely managing the processes efficiently. Further, it is possible to predict a shipment date if more orders are received, based on the ratio of the load against the capability, thus deciding whether the orders should be accepted or not.
These and other objects, advantages and features of the present invention will become more apparent from the following description and the accompanying drawings.